- Leetcode 357.Count Number With U
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- 357. Count Numbers with Unique D
- Leetcode 357. Count Numbers with
Given anon-negativeinteger n, count all numbers with unique digits, x, where 0 ≤ x < 10n.
Example:
Given n = 2, return 91. (The answer should be the total numbers in the range of 0 ≤ x < 100, excluding[11,22,33,44,55,66,77,88,99])
数每位都没有重复数字的个数
显然1 有10中选择， 2位数 第一位有9种， 第二位有9种， 总共有9*9
n==3： 前两位有9*9， 第三位有10-2 = 8 种选择 总共9*9*8
以此类推
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